1. Field of the Invention
The present invention is directed to computer tomography devices, and in particular to such devices having a radiation detector which is stationary or mutating.
2. Description of the Prior Art
In a Conventional computer tomography device, a source of penetrating radiation, such as an x-ray tube, emits a fan-shaped radiation beam. A row of detector elements is provided for detecting radiation attenuated by an examination subject disposed between the source of penetrating radiation and the detector row. The radiation source and/or detector are mounted on a live ring which is rotated around the examination subject, or the radiation source is electronically rotated, so that a slice of the examination subject is irradiated from a large number of different angular directions. A computer then constructs a viewable image from the outputs of the detector elements.
In conventional computer tomography devices of this type, having a stationary radiation detector, the number of detector elements in the radiation detector is so low that image reconstruction when using the focus as the projection center would produce an unacceptable image resolution. The measured data for each detector element must be acquired and intermediately stored during the rotation of the radiation source, so that real-time measured data processing is not possible. Even if the hardware outlay were increased, by using a greater number of more narrow detector elements, such a computer tomography device would violate the sampling theorem, given the conventional reconstruction techniques wherein the focus of the radiation source is used as the image projection center, because each detector element would be more narrow than the center-to-center spacing of the detector elements.